bug#16111: (erc-current-logfile buf) behavior differs to with-current-buffer buf

[Ivan Shmakov]

Package:  emacs
Severity: minor

        My guess is that the results of (erc-current-logfile buffer) and
        (with-current-buffer buffer (erc-current-logfile)) were intended
        to be the same.  However, as the function references the session
        buffer-local variables (erc-session-server, erc-session-port,
        and, indirectly, erc-server-current-nick and erc-server-process)
        /without/ switching to the buffer given, the results are
        somewhat undefined.

(defun erc-current-logfile (&optional buffer)
  "Return the logfile to use for BUFFER.
If BUFFER is nil, the value of `current-buffer' is used.
This is determined by `erc-generate-log-file-name-function'.
The result is converted to lowercase, as IRC is case-insensitive"
  (unless buffer (setq buffer (current-buffer)))
  (let ((target (or (buffer-name buffer) (erc-default-target)))
        (nick (erc-current-nick))
        (server erc-session-server)
        (port erc-session-port))
    …))

        (There, it may make sense to enclose the most part of the code
        within a with-current-buffer form.)

        This may show no symptoms as long as erc-save-buffer-in-logs is
        called in either of the buffers belonging to the same session,
        but I’m in doubt that erc-log-save-all-buffers (which may run as
        part of kill-emacs-hook) will behave sensible in general.

-- 
FSF associate member #7257